As is known in the art, conventional high availability radar systems include at least two identical reference signal generation and distribution systems. Each component needing a reference signal receives a copy of the signal from each of the reference distribution systems to allow continued operation despite a failure in generating or distributing the reference signal. Components receiving the reference signal are called sinks herein.
FIG. 1 shows a prior art signal distribution system 100 having first and second identical signal sources 112a, b, each driving a respective one of first and second identical active splitters 114a, b. A first signal generation and distribution system comprises the first signal source 112a and the first active splitter 114a, and a second signal generation and distribution system comprises the second signal source 112b and the second active splitter 114b. Signal sinks 116a-N receive signals from both the first and second signal generation and distribution systems. As can be seen, the redundant signal distribution systems enable the sinks to receive a reference signal while meeting a required availability despite failures.
There are a number of disadvantages to this traditional approach. One disadvantage is the cost of duplicating distribution and reception systems. A technical disadvantage is that the two distribution systems necessarily differ in manufacturing tolerances and errors, requiring radar calibration for each system, thus increasing the amount of radar timeline occupancy required to calibrate the radar. Radar calibration refers to the continuous process whereby hardware imperfections are compensated for to enable the radar to generate sharp beams with low sidelobes and deep nulls, despite manufacturing variations and subsequent changes due to component aging, temperature variation, power supply voltage variation, and the like.
Another disadvantage is that prior-art signal distribution systems include active components, thus reducing reliability and increasing cost, complexity and sensitivity to temperature variations. Yet another disadvantage is that each and every component requiring a reference signal must be equipped to accept and choose between or combine at least two reference signals, thus at least doubling the expense and complexity of the component's signal reception interface.
There are alternate prior-art approaches where a single distribution system is driven by a pair of sources through a complicated redundant switching arrangement, but it can be difficult to find an adequate approach because the switches themselves are active and/or mechanical, and thus of limited reliability.